#include "MD5.h"
#include <cstring>

#define F(x, y, z) (((x) & (y)) | ((~x) & (z)))
#define G(x, y, z) (((x) & (z)) | ((y) & (~z)))
#define H(x, y, z) ((x) ^ (y) ^ (z))
#define I(x, y, z) ((y) ^ ((x) | (~z)))
#define ROTATE_LEFT(x, n) (((x) << (n)) | ((x) >> (32-(n))))
#define FF(a, b, c, d, x, s, ac) { \
 (a) += F ((b), (c), (d)) + (x) + (uint32_t)(ac); \
 (a) = ROTATE_LEFT ((a), (s)); \
 (a) += (b); \
}
#define GG(a, b, c, d, x, s, ac) { \
 (a) += G ((b), (c), (d)) + (x) + (uint32_t)(ac); \
 (a) = ROTATE_LEFT ((a), (s)); \
 (a) += (b); \
}
#define HH(a, b, c, d, x, s, ac) { \
 (a) += H ((b), (c), (d)) + (x) + (uint32_t)(ac); \
 (a) = ROTATE_LEFT ((a), (s)); \
 (a) += (b); \
}
#define II(a, b, c, d, x, s, ac) { \
 (a) += I ((b), (c), (d)) + (x) + (uint32_t)(ac); \
 (a) = ROTATE_LEFT ((a), (s)); \
 (a) += (b); \
}

MD5::MD5() { reset(); }

void MD5::reset() {
    count[0] = count[1] = 0;
    state[0] = 0x67452301;
    state[1] = 0xefcdab89;
    state[2] = 0x98badcfe;
    state[3] = 0x10325476;
    finished = false;
}

void MD5::update(const unsigned char* input, size_t inputLen) {
    size_t i, index, partLen;
    index = (unsigned int)((count[0] >> 3) & 0x3F);
    if ((count[0] += ((uint32_t)inputLen << 3)) < ((uint32_t)inputLen << 3))
        count[1]++;
    count[1] += ((uint32_t)inputLen >> 29);
    partLen = 64 - index;
    if (inputLen >= partLen) {
        memcpy(&buffer[index], input, partLen);
        transform(buffer);
        for (i = partLen; i + 63 < inputLen; i += 64)
            transform(&input[i]);
        index = 0;
    } else {
        i = 0;
    }
    memcpy(&buffer[index], &input[i], inputLen - i);
}

void MD5::final(unsigned char digest[16]) {
    if (finished) return;
    unsigned char bits[8];
    static unsigned char PADDING[64] = { 0x80 };
    encode(bits, count, 8);
    size_t index = (unsigned int)((count[0] >> 3) & 0x3f);
    size_t padLen = (index < 56) ? (56 - index) : (120 - index);
    update(PADDING, padLen);
    update(bits, 8);
    encode(digest, state, 16);
    finished = true;
}

void MD5::transform(const unsigned char block[64]) {
    uint32_t a = state[0], b = state[1], c = state[2], d = state[3], x[16];
    decode(x, block, 64);
    FF(a, b, c, d, x[ 0],  7, 0xd76aa478); FF(d, a, b, c, x[ 1], 12, 0xe8c7b756);
    FF(c, d, a, b, x[ 2], 17, 0x242070db); FF(b, c, d, a, x[ 3], 22, 0xc1bdceee);
    FF(a, b, c, d, x[ 4],  7, 0xf57c0faf); FF(d, a, b, c, x[ 5], 12, 0x4787c62a);
    FF(c, d, a, b, x[ 6], 17, 0xa8304613); FF(b, c, d, a, x[ 7], 22, 0xfd469501);
    FF(a, b, c, d, x[ 8],  7, 0x698098d8); FF(d, a, b, c, x[ 9], 12, 0x8b44f7af);
    FF(c, d, a, b, x[10], 17, 0xffff5bb1); FF(b, c, d, a, x[11], 22, 0x895cd7be);
    FF(a, b, c, d, x[12],  7, 0x6b901122); FF(d, a, b, c, x[13], 12, 0xfd987193);
    FF(c, d, a, b, x[14], 17, 0xa679438e); FF(b, c, d, a, x[15], 22, 0x49b40821);
    GG(a, b, c, d, x[ 1],  5, 0xf61e2562); GG(d, a, b, c, x[ 6],  9, 0xc040b340);
    GG(c, d, a, b, x[11], 14, 0x265e5a51); GG(b, c, d, a, x[ 0], 20, 0xe9b6c7aa);
    GG(a, b, c, d, x[ 5],  5, 0xd62f105d); GG(d, a, b, c, x[10],  9, 0x02441453);
    GG(c, d, a, b, x[15], 14, 0xd8a1e681); GG(b, c, d, a, x[ 4], 20, 0xe7d3fbc8);
    GG(a, b, c, d, x[ 9],  5, 0x21e1cde6); GG(d, a, b, c, x[14],  9, 0xc33707d6);
    GG(c, d, a, b, x[ 3], 14, 0xf4d50d87); GG(b, c, d, a, x[ 8], 20, 0x455a14ed);
    GG(a, b, c, d, x[13],  5, 0xa9e3e905); GG(d, a, b, c, x[ 2],  9, 0xfcefa3f8);
    GG(c, d, a, b, x[ 7], 14, 0x676f02d9); GG(b, c, d, a, x[12], 20, 0x8d2a4c8a);
    HH(a, b, c, d, x[ 5],  4, 0xfffa3942); HH(d, a, b, c, x[ 8], 11, 0x8771f681);
    HH(c, d, a, b, x[11], 16, 0x6d9d6122); HH(b, c, d, a, x[14], 23, 0xfde5380c);
    HH(a, b, c, d, x[ 1],  4, 0xa4beea44); HH(d, a, b, c, x[ 4], 11, 0x4bdecfa9);
    HH(c, d, a, b, x[ 7], 16, 0xf6bb4b60); HH(b, c, d, a, x[10], 23, 0xbebfbc70);
    HH(a, b, c, d, x[13],  4, 0x289b7ec6); HH(d, a, b, c, x[ 0], 11, 0xeaa127fa);
    HH(c, d, a, b, x[ 3], 16, 0xd4ef3085); HH(b, c, d, a, x[ 6], 23, 0x04881d05);
    HH(a, b, c, d, x[ 9],  4, 0xd9d4d039); HH(d, a, b, c, x[12], 11, 0xe6db99e5);
    HH(c, d, a, b, x[15], 16, 0x1fa27cf8); HH(b, c, d, a, x[ 2], 23, 0xc4ac5665);
    II(a, b, c, d, x[ 0],  6, 0xf4292244); II(d, a, b, c, x[ 7], 10, 0x432aff97);
    II(c, d, a, b, x[14], 15, 0xab9423a7); II(b, c, d, a, x[ 5], 21, 0xfc93a039);
    II(a, b, c, d, x[12],  6, 0x655b59c3); II(d, a, b, c, x[ 3], 10, 0x8f0ccc92);
    II(c, d, c, d, x[10], 15, 0xffeff47d); II(b, c, d, a, x[ 1], 21, 0x85845dd1);
    II(a, b, c, d, x[ 8],  6, 0x6fa87e4f); II(d, a, b, c, x[15], 10, 0xfe2ce6e0);
    II(c, d, a, b, x[ 6], 15, 0xa3014314); II(b, c, d, a, x[13], 21, 0x4e0811a1);
    II(a, b, c, d, x[ 4],  6, 0xf7537e82); II(d, a, b, c, x[11], 10, 0xbd3af235);
    II(c, d, a, b, x[ 2], 15, 0x2ad7d2bb); II(b, c, d, a, x[ 9], 21, 0xeb86d391);
    state[0] += a;
    state[1] += b;
    state[2] += c;
    state[3] += d;
}

void MD5::encode(unsigned char* output, const uint32_t* input, size_t len) {
    for (size_t i = 0, j = 0; j < len; i++, j += 4) {
        output[j] = (unsigned char)(input[i] & 0xff);
        output[j+1] = (unsigned char)((input[i] >> 8) & 0xff);
        output[j+2] = (unsigned char)((input[i] >> 16) & 0xff);
        output[j+3] = (unsigned char)((input[i] >> 24) & 0xff);
    }
}

void MD5::decode(uint32_t* output, const unsigned char* input, size_t len) {
    for (size_t i = 0, j = 0; j < len; i++, j += 4)
        output[i] = ((uint32_t)input[j]) | (((uint32_t)input[j+1]) << 8) |
                    (((uint32_t)input[j+2]) << 16) | (((uint32_t)input[j+3]) << 24);
} 